Algebra · real student question

Solve 4x - 0.35(x - 1) = 220.6 for x.

Question

Solve for xx:

4x0.35(x1)=220.64x-0.35(x-1)=220.6

Step-by-step solution

  1. Distribute before doing anything else. Removing the bracket correctly is the only real difficulty here:

    4x0.35(x1)=4x0.35x+0.354x-0.35(x-1)=4x-0.35x+0.35

  2. Combine into a single linear expression.

    4x0.35x=3.65x3.65x+0.35=220.64x-0.35x=3.65x\quad\Rightarrow\quad 3.65x+0.35=220.6

    The left side is now the standard form mx+bmx+b with m=3.65m=3.65 and b=0.35b=0.35.

  3. Move the constant across.

    3.65x=220.60.35=220.253.65x=220.6-0.35=220.25

    Writing 220.6220.6 as 220.60220.60 first makes this subtraction hard to get wrong.

  4. Divide, clearing the decimals first.

    x=220.253.65=22025365=440573x=\frac{220.25}{3.65}=\frac{22025}{365}=\frac{4405}{73}

    (Both numerator and denominator were multiplied by 100100, then divided by their common factor 55.)

  5. Express as a decimal and check. 7360=438073\cdot 60=4380, remainder 2525, so x=60+2573=60.342466x=60+\frac{25}{73}=60.342466\ldots Substituting: 3.6560.342466=220.253.65\cdot 60.342466=220.25, and 220.25+0.35=220.60220.25+0.35=220.60. The original equation holds, so x=44057360.3425x=\frac{4405}{73}\approx 60.3425.

Answer

x=44057360.3425x=\frac{4405}{73}\approx 60.3425

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